Here is a "speed racer" screen grab (1965) which clearly shows that their artists came up with the new challenger first.
Pictured below is what I drove in high school though mine had the SS appearance package.
I pulled the original LS1 and installed a L88 that had been built for 750hp but changed the pistons and had a cam grinder reduce lift and duration slightly.
Cam was so "big" he was also able to change lobe centers to get me a decent idle without losing too much top end.
With a holley 950 three barrel, it would pull to 7000.......with a modified quadrajet, it pulled to 7250 in top gear with 3.07 gears and 255/60 "blue streak specials".
Fast enough to win every mile race I was in.
The quadrajet could actually flow over 1000cfm but I limited the air door on the secondaries so it would get a better "signal" in order to get more consistent mixture ratio.
It probably flowed around 830cfm with the snappy response of the tiny primaries.
The guy who built the L88 was a neighbor who had died at riverside in a Porsche when his thinwall roll cage collapsed.
I bought it more or less complete from his widow for 500 bucks.
I had the rear wheels widened later on to 10 inches which they did by welding a band in the center after lathing off the lips.
There was a picture of it in the Miami herald with a kid in a canoe paddling past it after hurricane david........which is how I snagged it for 400 bucks.
It had a water line on the rear view mirror and even the 4 speaker factory stereo still worked after I dried it out.
When I was fixing it up, I found some papers woven into the seat springs that showed it had been through the assembly line for impala SS appearance package, F41 suspension and other goodies and the previous owner still had the window sticker which read around $4800 bucks.........which was very expensive for November 1968 sales.
I tracked down the original owner and he was Mr Luby of Luby Chevrolet who had it specially built as his demo and he drove it for a couple of years.
Possibly the only "SS427 caprice" ever made.
Wish I still had it.
I still do mile racing and the irony is that it's only a couple of miles from where I used to mile race on the street in high school.